The invention relates to a shaft rotating device for rotating a shaft of a medical instrument about its longitudinal axis relative to a handle of the medical instrument.
The invention further relates to a medical instrument for endoscopic surgery, comprising a shaft and a handle, wherein the handle is arranged at a proximal portion of the shaft.
A shaft rotating device is, for example, known from the firm catalogue of Karl Storz GmbH & Co., Tuttlingen, “Karl Storz—Endoskope, Laparoskopie”, 5. edition 1/2005, page SCC-INTRO 5B. This brochure shows a handle for the laparoscopy with the product number 33131 or 30131 which comprises the known shaft rotating device.
The medical instrument comprising the known shaft rotating device is used for endoscopic operations in the field of the minimally invasive surgery, during which abnormal tissue of e.g. the appendix, the bladder etc. is removed. The present invention, however, is not limited to a use of the shaft rotating device in such a medical instrument.
The known medical instrument comprises an elongated hollow shaft, at whose proximal portion a handle for operation by the surgeon is arranged. A distal portion of the shaft is introduced into a cavity of a patient during the operation, at which jaws are pivotably arranged for grasping and/or cutting tissue. At least one jaw is in driving connection with the handle via a thin pull/push rod for controlling its grasping and/or cutting capability. At the proximal portion of the shaft a shaft rotating device is arranged, which allows the shaft rotating about its longitudinal axis relative to the handle. Upon rotating the shaft, the position of the jaws relative to the tissue can be adapted in the best way regarding the requirements of the operation.
The proximal portion of the shaft is rotationally fixedly accommodated in an opening of the handle. As an outer diameter of the shaft is slightly larger than an inner diameter of the opening, an outer surface of the shaft and an inner surface of the handle are in frictional contact. The known shaft rotation device further comprises an operating element being rotationally fixed at the shaft. Upon operating the operating element, the surgeon can rotate the shaft relative to the handle by a small angular range against the frictional forces. In turn, when outer forces affect the distal portion of the shaft during the operation, an undesired rotation of the shaft relative to the handle is prevented due to the large frictional forces between the surfaces of the shaft and the handle.
It is a disadvantage of the known shaft rotating device, that large frictional forces are required to fix the shaft rotationally stationary with respect to the handle during the operation. For rotating the shaft relative to the handle, these frictional forces have to be overcome, which requires a large torque applied to the operating element during the shaft of the medical instrument being introduced into the body cavity. This aggravates the handling of the instrument and increases the risk of injuries for the patient during the operation.
Furthermore, it is disadvantageous, that the strength of the torque applied to the operating element depends on the frictional forces between the surfaces of the shaft and the handle. In case of small production variations regarding e.g. the materials and dimensions of the shaft and the handle, a torque with a different strength has to be exerted by the surgeon on the operating element. Therefore using such a medical instrument requires the surgeon not only to be experienced with this medical instrument, but also to adapt himself to a medical instrument with a shaft rotating device having slightly different frictional forces.
Moreover, the known shaft rotating device has the drawback, that rotating the shaft against the frictional forces requires a huge physical effort by the surgeon during the operation. The operation is thus physically exhausting for the surgeon, which increases the possibility of unintentional malpractices of the surgeon.
A further disadvantage of the known shaft rotating device is, that any rotation of the shaft relative to the handle mechanically affects the surfaces of the involved components in terms of polishing them, so that these surfaces turn smooth. As a result, the frictional forces between the shaft and the handle can decrease to an extent that the shaft can rotate in undesired fashion, when small external torques are applied to the shaft.